This invention relates to noninvasive physiologic condition sensors, and more particularly, to noninvasive pulse oximetry sensors.
Noninvasive pulse oximetry typically takes advantage of the difference in the red and infrared light absorption coefficient of unoxygenated hemoglobin and oxygenated hemoglobin. This type of oximetry is normally conducted using sensors placed on the tissue of a patient. The sensors normally include a source for emitting light at one or more wavelengths placed on one side of a patient""s tissue and a photodetector for detecting the amount of light which passes through the patient""s tissue on the opposite side of the patient""s tissue. The amount of light absorbed at each wavelength is used to calculate oxygen saturation in the patient""s blood in accordance with Lambert-Beer""s law. Such sensors are normally placed on the toe, foot, fingertip, ear lobe, nasal septum or forehead of the patient and preferably include means for retaining the sensor in position for the extended periods during which such measurements are made.
One type of prior art pulse oximetry sensor is disclosed in U.S. Pat. No. 6,061,584, the disclosure of which is incorporated by reference herein.
According to the present invention, a physiologic condition sensor comprises a sensor body including an optical assembly housed in an internal cavity of a sensor housing. The optical assembly includes a light emitting diode (LED) mounted at one end of a substrate and a photodetector mounted at the other. The optical assembly is configured to include a head portion, a tail portion, and an intermediate portion connecting the head portion and tail portion. The head and tail portions are wider than the intermediate portion to conform to the patient""s anatomy and to prevent longitudinal deformation of the sensor housing around the optical assembly.
In a preferred embodiment, the sensor housing comprises a base and a cover. The base is configured to include a channel into which the optical assembly snuggly nests. This facilitates a tight fit of the optical assembly in the sensor housing and provides easy and exacting assembly of the sensor body. The cover is configured to include a plateau that fits within the channel in the base and cooperates with the channel to further provide a secure enclosure for the optical assembly.
In a preferred embodiment, lugs and posts formed in the channel, which cooperate with rooms and holes formed in the cover, engage the optical assembly to prevent longitudinal deformation of the cover and base of the sensor housing around the optical assembly. The seam at which the cover and base meet is configured to lie on a sidewall of the sensor body to give a uniform and seamless look to the sensor.
Additional features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.